I. Field of the Invention
This invention relates generally to apparatus for facilitating placement of an over-the-wire, left ventricular lead in a patient, and more particularly to a hemostasis valve for creating a fluid-tight seal with a proximal lead terminal of a left ventricular pacing lead and with a guidewire used during a lead implant procedure.
II. Discussion of the Prior Art
In treating heart failure patients with cardiac stimulation, it is necessary to install a stimulating/sensing lead on the left side of the heart. However, placement of the lead itself into the left ventricle is to be avoided. A procedure has been perfected for advancing a very small diameter lead through the coronary sinus and down a coronary vein on the left side of the heart whereby electrical stimulation of myocardial tissue of the left ventricle can be achieved. Because the lead must necessarily be of a small diameter and be highly flexible, it lacks steerability. Therefore, a guidewire is used to facilitate routing of the lead. The guidewire is advanced through the vascular system until its distal end enters the target coronary vein. The stimulating lead is tubular in configuration, allowing it to be slipped over the guidewire and advanced by pushing until its distal electrode(s) are at a desired location on the left ventricle.
In that the lead is tubular, blood can flow through its lumen and if clotting occurs, it may prove difficult to extract the guidewire without dislodging the lead. If blood is allowed to exit the proximal end of the lead, it can create a mess for the surgeon or cardiologist to deal with.
Accordingly, there is a need for a hemostasis valve that can be used to prevent blood or other fluid loss during lead implant procedures involving over-the-wire cardiac stimulating leads and which can be used to prevent clotting in the lumen of the lead.
The prior art discloses a variety of catheter introducers incorporating hemostasis valves, whereby blood loss along the outside diameter of a guidewire or diagnostic or angioplasty catheter is prevented. The Stevens U.S. Pat. Nos. 5,693,025 and 5,935,112 are exemplary. They each include a resilient rubber seal member having an aperture therethrough for receiving a guidewire and a collar that when screwed down on the proximal end of the device compresses the seal member tightly against the guidewire. A further collet-like clamp is provided at the distal end of the Stevens"" introducer to provide a way of clamping the device in place on a proximal end of a catheter. The introducer of the prior art Stevens patent also includes provision for introducing a fluid or some other medical device into the patient""s body.
U.S. Pat. No. 6,142,981 to Heck et al. describes a cannula having a hemostasis valve thereon that incorporates an elastomeric seal having a self-closing aperture which, when forced open by a guidewire or the like, seals about the guidewire to prevent blood loss therealong. No provision is made for clamping the distal end of the cannula to a catheter or stimulating lead. Thus, the device described in the Heck ""981 patent is similar in most respects to the hemostasis cannula valve described in the Stevens U.S. Pat. No. 5,643,227 and the Davila et al. U.S. Pat. No. 5,520,655.
The present invention is directed to a hemostasis valve for use in introducing an over-the-wire medical lead into a subject""s vascular system. An over-the-wire lead comprises a lead body with a distal end, a proximal end and a lumen that extends between the two ends. Affixed to the proximal end of the lead body is a tubular connector terminal that is adapted to mate with contacts in the header of a cardiac rhythm management device, such as a pacemaker or defibrillator. The hemostasis valve itself comprises a molded plastic housing having a passageway therein with first and second openings in communication with the passageway. An elastomeric, pierceable, seal member is carried by the housing for sealing the first opening. A resilient annular tip surrounds the second opening and it itself has a central opening sized to receive the tubular connector terminal at the proximal end of the lead body therein with a predetermined friction fit for both gripping and sealing the tubular connector terminal with respect to the housing. This design obviates the need for a screw-type clamp at opposed ends of the housing, one for establishing a seal to the guidewire and the other for establishing a seal to the lead""s tubular connector terminal.